Bonding method employing an inorganic adhesive composition

ABSTRACT

Disclosed is an inorganic adhesive composition comprising (a) an aqueous silica sol and (b) an inorganic refractory powder along with one or more material selected from (c) a fine powdery silica, (d) an aqueous alkali silicate solution and (e) a silane coupling agent. After hardening, the hardened product of the composition displays noticeably improved adhesion strength and electric insulating property.

FIELD OF THE INVENTION

The present invention relates to (an improvement) of an inorganiccomposition comprising an aqueous silica sol and an inorganic refractorypowder. The composition of the present invention changes via drying to ahardened product which shows remarkably excellent properties in electricinsulation and adhesion between various materials such as ceramics,glass, slates, aluminium, stainless steel, iron and other metals.

BACKGROUND OF THE INVENTION

JP-B-39-8547 (the term "JP-B" as used herein means an "examined Japanesepatent publication") discloses an improved adhesive for electricappliances, which contains an aqueous silica sol (such as silica powder)having a particle size of from 5 to 150 microns and metal oxide such asboron oxide, lead oxide, antimony troxide or the like.

JP-A-48-93636 (the term "JP-A" as used herein means an "unexaminedpublished Japanese patent application") discloses a compositioncomprising an acidic silica sol having a particle size of from 7 to 150millimicrons, an aqueous solution for crystalloid silicate which is freefrom alkali metal ion and an inorganic refractory powder.

JP-B-56-38544 discloses an inorganic composition comprising an aqueoussilica sol and an inorganic fiber or refractory powder having a particlesize of from 0.1 micron to 20 microns along with pigment, aggregate andother aids.

Hardened products of adhesive compositions containing a silica sol and arefractory powder, but not containing any vitrifying components, lacksufficient adhesive strength though displaying a high heat-resistance.

An adhesive comprising from 20 to 70 parts of an aqueous silica solhaving a concentration of from 2 to 40%, from 30 to 95 parts of talc,silica, mica, sillimanite, asbestos, clay, glass for electricinsulation, synthetic mica, magnesium silicate, aluminium silicate,magnesium oxide, aluminium oxide or the like powder having a particlesize of from 5 to 150 microns, and from 10 to 100 parts of boron oxide,lead oxide, antimony trioxide or the like, which is described inJP-B-39-8547, must be subjected to stepwise heat-treatment to beeffected in the vicinity of 100° C., then 300° C. and then 600° C. inorder, after having been left to stand at room temperature for a while,when it is actually used for adhesion. Such stepwise heat treatmentprocess is not simple but is extremely complicated. Additionally, thehardened product of the adhesive vitrifies at a high temperature andtherefore the heat-resistance thereof is not sufficient.

The composition illustrated in the above-mentioned JP-A-48-93636, whichis composed of an acidic silica sol and a crystalloid silicate liquiddoes not have a sufficient storage stability, and it could not form anadhesive having a high adhesion strength. On the other hand, thecomposition illustrated in the above-mentioned JP-B-56-38544, which iscomposed of an aqueous silica sol, an inorganic fiber and a refractorypowder, could not form an adhesive having a sufficient electricinsulating property.

Additionally, it has been found that the hardened products of theconventional adhesives adsorb water from the aerial atmosphere tothereby gradually lower the adhesion strength.

Where an adhesive containing a silica sol and a refractory powder isapplied to adhesion of various materials, only solution of theabove-mentioned problems on the adhesion strength, long-time storagestability and heat-resistance is still insufficient and the adhesive isdesired to have further additional higher properties. For instance, whenan adhesive is to be fully filled even to fine slits between substancesto be bonded with the adhesive by the use of an automaticadhesive-injector, the adhesive to be used for the purpose is desired tohave a high fluidity and a good workability. Specifically, thedispersion stability of the adhesive is indispensable so that thecomponents of the adhesive do neither precipitate nor coagulate duringhandling it.

In addition, where an adhesive is hardened by drying, the hardenedproduct is desired to be free from uneven shrinkage, cracking andfoaming. That is, the adhesive is desired to have a good hardeningproperty.

On the other hand, where the parts as bonded via an adhesive are exposedto temperature variation between a low temperature condition and a hightemperature condition in practical use thereof, the adhesive used isdesired to have an extremely high adhesion strength and additionally thehardened adhesive layer between the parts as bonded therewith is furtherdesired to have a properly controlled thermal expansion coefficient. Inparticular, in an electric-light bulb or an electric heater, the jointpart between the bulb glass or jacket glass to cover the heating elementand the lamp base is exposed to such a temperature variation in anextremely short period of time, or that is, it is exposed to a so-calledheat shock. Accordingly, the adhesive to be applied to such a joint partis indispensable to have a sufficient heat-shock resistance enough to beresistant to repeated heat-shock of the kind without breakage of thebonded joint part.

Additionally, where at least one part of the parts to be bonded with anadhesive is a metal material, the adhesive is desired to be free fromcorrosion of the metal material because of the hardened adhesive layerduring practical use.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the above-mentionedproblems in the conventional adhesive compositions and to provide anovel inorganic composition to be able to give an adhesive which has ahigh electric insulating property and a high adhesion strength and whichmay satisfactorily bond materials of the same kind or different kindssuch as ceramics, glass, slates, hardened cement products, aluminium,stainless steel, iron, and other various metal materials. The adhesivederived from the composition of the invention is free from lowering ofthe adhesion strength even after absorption of water.

Specifically, the present invention provides an inorganic adhesivecomposition which comprises the following components (a) and (b) andadditionally the following component (c) or (e), or additionally twocomponents of (c) and (d), or (c) and (e), or (d) and (e), oradditionally three components of (c), (d) and (e), the total solidcontent based on the components being from 40 to 95% by weight. Thecomposition is stable and has a viscosity of from 1 to 10000 poise at20° C.

(a) An aqueous silica sol having a mean particle size of from 5 to 200millimicrons and having a molar ratio of SiO₂ /M₂ O of being from 30 to2000, where M represents an alkali metal atom, an amine molecule or aquaternary ammonium group.

(b) An inorganic refractory powder having a particle size of from 0.5 to1000 microns.

(c) A fine powder of silica having a particle size of from 5 to 400millimicrons.

(d) An aqueous solution of an alkali silicate having a molar ratio ofSiO₂ /M'₂ O of being from 1 to 30 and having a concentration of from 1to 60% by weight, where M' represents Na, K, Li, an amine molecule or aquaternary ammonium group.

(e) One or more coupling agents selected from the group consisting of asilane compound of the formula (I):

    R.sup.1 Si(OR).sub.3                                       (I)

wherein OR is an alkoxy or acyloxy group having from 1 to 3 carbonatoms, and R¹ represents a monovalent organic group having from 2 to 9carbon atoms, or a hydrolysate thereof, and a silane compound of theformula (II):

    R.sup.1 SiCH.sub.3 (OR).sub.2                              (II)

wherein OR and R¹ have the same meanings as defined above, or ahydrolysate thereof.

The first preferred embodiment of the adhesive composition of thepresent invention comprises 100 parts by weight as SiO₂ of the aqueoussilica sol (a), from 100 to 20000 parts by weight of the inorganicrefractory powder (b), and from 0.2 to 200 parts by weight of the finesilica powder (c).

The second preferred embodiment of the adhesive composition of thepresent invention comprises 100 parts by weight as SiO₂ of the aqueoussilica sol (a), from 100 to 100000 parts by weight of the inorganicrefractory powder (b), from 0.5 to 500 parts by weight of the finesilica powder (c), and from 0.1 to 500 parts by weight as the alkalisilicate component of the aqueous alkali silicate solution of (d).

The third preferred embodiment of the adhesive composition of thepresent invention comprises 100 parts by weight as SiO₂ of the aqueoussilica sol (a), from 50 to 10000 parts by weight of the inorganicrefractory powder (b), and from 0.05 to 500 parts by weight of one ormore coupling agents (e).

The fourth preferred embodiment of the adhesive composition of thepresent invention comprises 100 parts by weight as SiO₂ of the aqueoussilica sol (a), from 100 to 100000 parts by weight of the inorganicrefractory powder (b), from 0.5 to 500 parts by weight of the finesilica powder (c), and from 0.05 to 500 parts by weight of one or morecoupling agents (e).

The fifth preferred embodiment of the adhesive composition of thepresent invention comprises 100 parts by weight as SiO₂ of the aqueoussilica sol (a), from 100 to 100000 parts by weight of the inorganicrefractory powder (b), from 0.1 to 500 parts by weight as the alkalisilicate component of the aqueous alkali silicate solution (d), and from0.05 to 500 parts by weight of the one or more of the coupling agents(e).

The sixth preferred embodiment of the adhesive composition of thepresent invention comprises 100 parts by weight as SiO₂ of the aqueoussilica sol (a), from 100 to 100000 parts by weight of the inorganicrefractory powder (b), from 0.5 to 500 parts by weight of the finesilica powder (c), from 0.1 to 500 parts by weight as the alkalisilicate component of the aqueous alkali silicate solution (d), and from0.05 to 500 parts by weight of one or more of the coupling agents (e).

DETAILED DESCRIPTION OF THE INVENTION

The aqueous silica sol (a) to be employed in the present invention isobtained with ease by known methods, for example, by way of treating adiluted aqueous solution of water glass with a cation-exchange substancefor removal of alkali therefrom or by way of neutralizing the waterglass with an acid followed by deflocculating of the silica, and it isgenerally in the form of a stable dispersion liquid where a colloidalsilica is stably dispersed in a medium of water. The colloidal silicamay have a mean particle size of from 5 to 200 millimicrons, preferablyfrom 10 to 150 millimicrons. The shape of the colloidal silica particlesmay be either spherical or non-spherical. The aqueous silica sol may beeither alkaline or acidic. The sol is preferred to have a molar ratio ofSiO₂ /M₂ O of being from approximately 30 to 2000, where M has the samemeaning as defined above. Examples of amines to be in the sol includemethylamine, ethylamine, triethanolamine, other ethanolamine and thelike; and those of quaternary ammonium groups therein includetetramethylammonium, monomethyltriethanolammonium,isopropyltriethanolammonium, tetraethanolammonium and the like. It ispreferable that the aqueous silica sol has an SiO₂ concentration of fromapproximately 1 to 50% by weight. It is also preferable to use a mixturecomprising two or more aqueous silica sols each having a different meanparticle size for obtaining a favorable composition.

The fine powdery silica (c) to be employed in the present inventionpreferably has a particle size of from 5 to 500 millimicrons, especiallypreferably from 5 to 200 millimicrons. The shape of the particles in thepowder may be either spherical or non-spherical. The particles may beeither crystalline or non-crystalline (amorphous), but they arepreferably non-crystalline. As methods of preparing the fine powderysilica (c), there are known, for example, a gas phase method of usingsilicon tetrachloride as a starting material and a neutralization methodof using sodium silicate as a starting material. Either of them can beemployed for preparing the fine powdery silica (c) for use in thepresent invention. The fine powdery silica may be used in the form of anaqueous suspension of the powdery silica.

The aqueous alkali silicate solution (d) which is employed in thepresent invention is an aqueous solution of a silicate of an alkalimetal such as lithium, sodium or potassium or of an amine or aquaternary ammonium. Examples of the amine include methylamine,ethylamine, triethanolamine, other ethanolamine and the like; andexamples of the quaternary ammonium include tetramethylammonium,monomethyltriethanolammonium, tetraethanolammonium and the like. Thealkali silicate has a molar ratio of SiO₂ /M'₂ O of being from 1 to 30,preferably from 1 to 10, where M' has the same meaning as defined above.The aqueous solution has a concentration of from 1 to 60% by weight,preferably from 5 to 50% by weight of the silicate. It may contain oneor more of the alkali silicates.

As examples of the inorganic refractory powder (b) for use in thepresent invention, there are mentioned powders of quartz, silica,feldspar, aluminium silicate, zirconium silicate, mullite, zirconia,alumina, silicon nitride, silicon carbide, talc, mica and the like. Theparticles in the powder may have a particle size of from approximately0.5 to 1000 microns, preferably from approximately 0.5 to 400 microns.Additionally, powders of glass fiber, potassium titanate fiber and thelike may also be employed, where the fibrous particles have a length offrom approximately 0.5 to 1000 microns and a diameter of fromapproximately 0.1 to 20 microns. These inorganic refractory powders maybe employed singly or as an admixture thereof.

The coupling agents (e) which are employed in the present invention aresilane compounds which are represented by the above-mentioned formula(I) or (II) and capable of forming two or three silanol groups in themolecule after hydrolysis, as well as hydrolysates of the compounds.Preferred examples of the agents includevinyltris(β-methoxyethoxy)silane CH₂ ═CHSi(OC₂ H₄ -OCH₃)₃,vinyltriethoxysilane CH₂ ═CHSi(OC₂ H₅)₃, vinyltrimethoxysilane CH₂═CHSi(OCH₃)₃, ##STR1## γ-aminopropyltriethoxysilane H₂ HC₃ H₆ Si(OC₂H₅)₃ or γ-anilinopropyltrimethoxysilane C₆ H₅ NHC₃ H₆ Si(OCH₃)₃ and thelike. Additionally, an aqueous solution of a hydrolysate to be obtainedby blending the silane compound and water may also be employed in thepresent invention.

The composition of the present invention can contain any other optionalcomponents in addition to the above-mentioned components, so far as itmay attain the objects of the present invention. Examples of additionalcomponents which may optionally be incorporated into the composition ofthe present invention are a powder of a bentonite clay mineral as anantisettling agent, as well as cellulose acetate, ethyl cellulose,hydroxyethyl cellulose, and synthetic organic polymers such as polyvinylpyrrolidone, polyvinyl alcohol and the like. A colorant may also beadded to the composition, which includes, for example, inorganic ororganic pigments for coloration, such as titanium oxide, iron oxide,chromium oxide or poster color.

For the purpose of enhancing the fluidity and the adhesion property ofthe composition, various kinds of surface active agents orsurface-treating agents as well as a small amount of hydrophilic organicsolvents such as methanol, ethanol or the like may also be added to thecomposition.

For blending the respective components to prepare the composition of theinvention, any known stirrers or mixers may be used and the componentsmay well be blended with ease.

In blending the components, they may be added to a container all at atime or one by one in any desired order.

Blending of the components is desired to be effected under the conditionof pertinent temperature and pressure so that the components are notdried during blending. For instance, the components are blended at atemperature of approximately 5° C. to 40° C. for a period of time ofapproximately 0.5 to 5 hours in an atmospheric condition to obtain apreferred composition.

As one preferred embodiment, the composition of the invention has asolid content of from approximately 40 to 95% by weight and has aviscosity of from 1 to 10000 poise at 20° C. Where it is stored in aclosed vessel at room temperature, it has a storage stability withoutdeteriorating for several months or more.

The composition of the present invention is hardened by drying at atemperature higher than the freezing temperature. Preferably, it ishardened by drying at a temperature of from 80° to 300° C. to obtain anespecially advantageous hardened product.

The interaction between the components in the composition of the presentinvention is complicated and could not completely be clarified up to thepresent. Anyway, it has been found that the second, fourth or fifthcomposition comprising (a) and (b) and additionally two components of(c) and (d), or (c) and (e), or (d) and (e) displays a more improvedadhesive capacity than the first or third composition comprising (a) and(b) and additionally (c) or (e); and the sixth composition comprising(a) and (b) and additionally three components of (c), (d) and (e)displays the most improved adhesive capacity. The interaction betweenthe plural components could be considered to be as follows:

Precisely, silica particles in the aqeuous silica sol have alkali ionsas adsorbed to the surfaces thereof for stabilizing the dispersion ofthe particles in the sol. Where the composition does not contain thefine powdery silica, the electric insulating resistance of the hardenedproduct of the composition gradually lowers with absorption of water inair immediately after drying, since the above-mentioned alkali ions mayfreely move in the hardened product under a high voltage condition.However, by adding the fine powdery silica, which has an extremely largespecific surface area, to the aqueous silica sol, the alkali ions in theaqueous silica sol are to be adsorbed to the surfaces of the fine silicaparticles in the fine powdery silica. As a result, the molar ratio ofSiO₂ /M₂ O (where M has the same meaning as mentioned above) is elevatedas a whole so that the electric insulating resistance of the hardenedproduct would not lower.

Additonally, the alkali silicate as added may cover the surface of thesilica particles in the aqueous silica sol, the particles in the finepowdery silica and the particles in the inorganic refractory powder sothat the specific surface area of the dried and hardened product of thecomposition is thereby noticeably reduced. As a result, the number ofthe --OH groups as existing in the unit surface area of the particleswould decrease so that the adsorption of water to the dried and hardenedproduct would be lowered. Because of these reasons, the electricinsulating property of the hardened product is considered to beimproved.

The silane compounds as represented by the above-mentioned formula (I)or (II) are, when added to the aqueous silica sol, brought into contactwith water contained in the sol so that the alkoxy group of the compoundis converted into a silanol group. The resulting silanol group ischemically or physically bonded to the surfaces of the colloidal silicaparticles, those of the powdery inorganic refractory particles and thoseof the fine powdery silica particles, during blending the compound withthe aqueous silica sol, the inorganic refractory powder and the finesilica powder. Where an aqueous solution of the hydrolysate of the saidsilane compound is employed, the same bonds are also formed. As aresult, in the blend system of the adhesive composition, thedispersibility of the inorganic refractory powder is noticeablyelevated; and the bonds between the colloidal silica particles with thesurfaces of the powdery inorganic refractory particles and those of thefine powdery silica particles extremely increase in the dried andhardened product from the adhesive composition. As a result, after thecomposition has been hardened to form a hardened product, the mechanicalstrength of the hardened product is extremely improved. The function ofthe silanol group to be derived by hydrolysis of the silane compoundshows itself also in the bonds between the surfaces of the substances tobe bonded with the adhesive and the colloidal silica particles becauseof the same reason as above. As a result, after the adhesive compositionas applied to the substances to be bonded therewith has been hardened,the bonding between the hardened product layer and the surfaces of thesubstances to be bonded is considered to be improved and elevatednoticeably. Precisely, the coupling agents of the present invention havea function of forming a hardened product layer which is dense and has anextremely improved mechanical strength and of extremely elevating thebonding strength between the hardened product layer and the surfaces ofthe substances to be bonded with the layer.

Additionally, improvement of the dispersibility of the inorganicrefractory powder because of the function of the silanol group to bederived by hydrolysis of the silane compounds results in improvement offluidity and workability of the composition of the invention. Moreover,the proportion of the inorganic refractory powder to the colloidalsilica in the composition may be increased because of the improvement ofthe dispersibility of the inorganic refractory powder and, as a result,uneven shrinkage, cracking or foaming which often occurs duringhardening of the adhesive composition could remarkably be inhibited andthe thermal expansion coefficient of the hardened product layer mayeasily be controlled.

Furthermore, the organic group as bonded to the silicon atom via thecarbon atom in the silane compound has a function of remarkably loweringthe water-absorption of the hardened product layer and of therebyelevating the electric insulating property of the layer.

Where a conventional adhesive composition comprising only an aqueoussilica sol and an inorganic refractory powder is used, the strength ofthe dried and hardened product layer would often be lower because ofadsorption of water to the layer so that the hardened adhesive layerwould often separate from the substrate substance. As opposed to this,water is hardly adsorbed to the hardened product layer to be formed fromthe adhesive composition of the present invention, such an unfavorablelowering of the strength of the hardened product layer does not occur.

However, if the particle size of the silica particles in the aqueoussilica sol is smaller than 5 millimicrons, the stability of thecomposition would be poor. On the other hand, if it is more than 200millimicrons, the silica particles in the aqueous sol would frequentlyprecipitate in the composition whereby the aqueous silica sol isineffective for expressing a high bonding powder.

If the molar ratio of SiO₂ /M.sub. 2 O (where M has the same meaning asdefined above) is less than 30, a part of the surfaces of the colloidalsilica particles would be dissolved with ease and the stability of thesol tends to be poor. Therefore, the molar ratio is preferably higher.However, a sol having a higher molar ratio than 2000 is hardly obtained.

If the SiO₂ concentration in the aqueous silica sol to be employed inthe present invention is too high, the stability of the sol is poor sothat the composition would become too thick and would therefore gelfrequently. However, if the SiO₂ concentration is too low, the bondingpower of the hardened product from the composition would be poor.Therefore, the preferred concentration range is from approximately 1 %by weight to 50% by weight.

The aqueous silica sol is preferably alkaline rather than acidic, sincethe former may impart a higher adhesive strength to the hardened productof the composition. It is desirable to employ a mixture comprisingplural aqueous silica sols each having a different mean particle size.This is because the filled density of the coagulated silica particles iselevated and a hardened product having a high adhesion strength may beobtained advantageously.

Where the fine powdery silica (c) to be employed in the presentinvention has a particle size of more than 400 millimicrons, it wouldhave a small specific surface area. However, if it is less than 5millimicrons, the particles could not exist stably. Accordingly, thefine powdery silica is to have a particle size of from approximately 5to 400 millimicrons, as being generally available and being expected tohave the intended effect.

However, in preparing the composition, when the proportion of the finepowdery silica is more than 500 parts by weight relative to 100 parts byweight as SiO₂ of the aqueous silica sol, the molar ratio of SiO₂ /M₂ O(where M has the same meaning as defined above) would rise too much sothat the stability of the composition would be lost. If, on the otherhand, it is less than 0.2 part by weight, a hardened product having ahigh electric insulating property could not be obtained.

The particle size of the particles of the refractory powder to be in thecomposition of the invention does not have any significant influence onthe properties of the adhesive composition itself, but the refractorypowder is advantageously a non-fibrous powder having a particle size offrom approximately 0.5 to 350 millimicrons or a fibrous powder having adiameter of from approximately 0.1 to 20 microns and a length of 1000microns or less. In particular, the refractory powder is preferably inthe form of a mixture comprising particles of plural types each having adifferent mean particle size so that the filled density of the hardenedproduct form the composition may be elevated. By adjusting the particlesize of the particles of the refractory powder to be employed in thepresent invention, a composition having a good workability can beobtained. However, if the proportion of the refractory powder is lessthan 50 parts by weight to 100 parts by weight of SiO₂ of the aqueoussilica sol, the shrinkage would be too large when the composition ishardened. That is, the hardened product would be ununiformly shrunk, orcracked, or foamed. On the contrary, if the proportion of the refractorypowder is more than 100000 parts by weight relative to 100 parts byweight of SiO₂ of the aqueous silica sol, the fluidity and theworkability of the adhesive composition would worsen. Additionally,since the amount of the colloidal silica would be relatively lowered, acomposition capable of forming a hardened adhesive product layer havinga high adhesion strength could not be obtained.

By further adding the aqueous alkali silicate solution, a more improvedadhesive composition can be obtained. If the molar ratio of SiO₂ /M'₂ O(where M' has the same meaning as defined above) of the aqueous alkalisilicate solution to be employed is more than 30, the alkali silicatewould have an insufficient capacity of covering the surfaces of theabove-mentioned refractory powder particles and fine silica particles.On the contrary, if the molar ratio of SiO₂ /M'₂ O is less than 1, thehardened product of the composition tends to absorb much more of waterand results lowering of the strength of the hardened products. If theconcentration of the aqueous alkali silicate solution to be added ismore than 60% by weight, the resulting composition would have a poorstability so that it would often be thickened or gelled. On the otherhand, if it is less than 1% by weight, the covering capacity over thesurfaces of the said particles would be poor.

Where the aqueous alkali silicate solution is added to the composition,if the solution is more than 500 parts by weight as the solid contentthereof to 100 parts by weight of SiO₂ of the aqueous silica sol, thecomposition would have a poor stability. However, if it is less than 0.1part by weight thereto, the effect by addition of the solution could notbe attained.

If the amount of the coupling agents to be added to the composition isless than 0.05 part by weight to 100 parts by weight of SiO₂ of theaqueous silica sol, a hardened product having the above-mentionedimproved properties could not be formed from the adhesive composition.On the contrary, if it is more than 500 parts by weight to 100 parts byweight of SiO₂ of the aqueous silica sol, the stability of the resultingadhesive composition would noticeably lower. In particular, it ispreferred to add the coupling agents in an amount of from 0.5 to 100parts by weight to 100 parts by weight of SiO₂ of the aqueous silicasol, so as to obtain a favorable adhesive composition.

In preparing the composition of the present invention by adding both theaqueous silica sol and the coupling agents thereto in the proportiondefined above, if the components are blended at a too high temperature,the resulting composition would be gelled. Therefore, the temperaturefor blending the composition is preferably approximately 40° C. orlower, more preferably room temperature. If the solid concentration inthe adhesive composition obtained by blending the constitutivecomponents mentioned above is too high, the composition may be dilutedwith water to obtain a desired composition having an intended solidconcentration.

The present invention will be explained in more detail by way of thefollowing examples, which, however, are not intended to restrict thescope of the present invention.

The following substance to be used in the following examples wereprepared. Precisely, (A₁) to (A₃) are commercial products of aqueoussilica sol; (A₄) is one prepared by diluting (A₁) with water; (B₁) to(B₄) are commercial products of inorganic refractory powder; (C₁) is acommercial product of fine powdery silica; (D₁) to (D₅) are commercialproducts of aqueous alkali silicate solution; and (E₁) to (E₅) arecommercial products of coupling agent.

(A₁): An alkaline aqueous sol having a particle size of colloidal silicaof being from 10 to 20 millimicrons, a molar ratio of SiO₂ /Na₂ O ofbeing 66, and an SiO₂ concentration of being 40% by weight.

(A₂): An alkaline aqueous sol having a particle size of colloidal silicaof being from 70 to 100 millimicrons, a molar ratio of SiO₂ /Na₂ O ofbeing 1300, and an SiO₂ concentration of being 40% by weight.

(A₃): An alcidic aqueous sol having a particle size of colloidal silicaof being from 10 to 20 millimicrons, a molar ratio of SiO₂ / Na₂ O ofbeing 500, and an SiO₂ concentration of being 20% by weight.

(A₄): alkaline aqueous sol as obtained by diluting

(A₁) with water and having an SiO₂ concentration of being 5% by weight.

(B₁): A quartz powder having a particle size distribution of from 0.5 to400 microns.

(B₂) : An alumina powder having a particle size distribution of from 0.5to 400 microns.

(B₃) A quartz powder having a particle size distribution of from 5 to150 microns.

(B₄): An alumina powder having a particle size distribution of from 5 to60 microns.

(C₁): A commercial fine powdery silica prepared by gas phase process andhaving a particle size of 12 millimicrons.

(D₁): An aqueous lithium silicate solution having a concentration of 20%by weight and a molar ratio of SiO₂ /Li₂ O of being 4.5.

(D₂): An aqueous quaternary ammonium silicate solution having aconcentration of 40% by weight and a molar ratio of SiO₂ / M'₂ O (whereM' represents a quaternary ammonium group) of being 14.0.

(D₃): An aqueous sodium silicate solution having a concentration of 30%by weight and a molar ratio of SiO₂ /Na₂ O of being 3.6.

(D₄): An aqueous potassium silicate solution having a concentration of30% by weight and a molar ratio of SiO₂ /K₂ O of being 4.0.

(D₅) : An aqueous sodium silicate solution obtained by diluting (D₃)with water and having a concentration of 5% by weight.

(E₁): γ-glycidoxypropyltrimethoxysilane.

(E₂): N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane.

(E₃) : Vinyltriacetoxysilane.

(E₄): γ-methacryloxypropyltrimethoxysilane.

(E₅): γ-glycidoxypropylmethyldiethoxysilane.

Properties of the composition as prepared in the following examples andthe hardened products derived therefrom were tested by the followingmethods.

Stability Test

A composition to be tested is stored in a closed glass container at 20°C. for 24 hours, and the fluidity of the thus stored composition wasvisually checked with the naked eye.

Workability Test

A composition to be tested is put in a glass container in an amount tohave a depth of 15 cm and then stored therein as it is at 20° C. for 24hours. Then a stainless steel bar having a diameter of 5 mm is insertedvertically into the composition, whereupon it is observed as to whetheror not the top edge of the bar could reach the bottom of the container.Accordingly, the presence or absence of the precipitated solid in thecomposition is checked.

Hardenability Test

A composition to be tested is coated over the complete surface of aglass sheet having a square of 20 mm×20 mm, the thickness of the coatedcomposition being 2 mm. Then, the thus coated glass sheet is put in adrier and dried at 110 ° C. for 30 minutes and thereafter taken outtherefrom. Presence or absence of cracks on the surface of the thushardened product is visually checked with the naked eye. Additionally,the pencile hardness of the surface of the hardened product is measured,whereupon the surface having a pencil hardness of 2H or higher isdetermined to be hard, whilst others having a lower hardness than theformer are determined to be insufficient (not hard).

Electric Insulating Property Test

A composition to be tested is put into a glass tube having an outerdiameter of 8 mm, an inner diameter of 6 mm and a length of 20 mm, andlead wires each having a diameter of 0.7 mm were inserted from thecenter part of the both ends of the tube in a depth of 5 mm. Thecomposition is then dried at 110° C. for 30 minutes and further heatedat 150° C. for 30 minutes, and then allowed to stand in a room having atemperature of 20° C. and a relative humidity of 90% for 24 hours.Afterwards, an voltage of 500 V is imparted from a direct currentbattery whereupon the electric resistance through the hardened productis measured.

Adhesion Strength Test

Two glass sheets each having a square of 20 mm×20 mm are bonded over thecomplete surfaces thereof via a composition to be tested. Then thecomposition is hardened by heating and drying at 110° to 150° C. for 30minutes and subsequently at 200° C. for 30 minutes, whereby the twosheets are bonded to each other. Next, fixing tools are attached to bothsides of the thus bonded glass sheets with a commercial high-strengthadhesive, and a tension is applied to the direction perpendicular to thebonded glass sheets by the use of a tensile tester at a speed of 1mm/min, whereupon the tension with which the bonded part of the glasssheets is broken is measured. Additionally, the broken surface of thebonded part is visually observed with the naked eye. "L" indicates thatthe bonded part was broken because of breakage of the adhesive layer;while "S" indicates that the bonded part was broken because ofseparation of the glass sheet from the adhesive layer.

EXAMPLE 1

An aqueous silica sol, a fine powdery silica and an inorganic refractorypowder, which are indicated in Table 1 below, were mixed in a mixer for2 hours at room temperature, to prepare compositions (Q₁) to (Q₅)mentioned in Table 1.

EXAMPLE 2

An aqueous silica sol, an aqueous alkali silicate solution, a finepowdery silica and an inorganic refractory powder, which are indicatedin Table 1 below, were mixed in a mixer for 3 hours at room temperature,to prepare compositions (Q₆) to (Q₁₉) mentioned in Table 1.

EXAMPLE 3

An aqueous silica sol, an aqueous alkali silicate solution, a finepowdery silica, an inorganic refractory powder and a silane couplingagent, which are indicated in Table 3 below, were mixed at roomtemperature for 3 hours, to prepare compositions (Q₂₀) to (Q₂₂).

Next, the properties of these compositions (Q₁) to (Q₂₂) and thehardened products thereof were tested in accordance with theabove-mentioned test methods. The results obtained are shown in Table 2and Table 4 below.

COMPARATIVE EXAMPLE 1

In the same manner as in Example 1, comparative compositions (R₁) to(R₄) were prepared, each comprising the components shown in Table 1.These were also tested by the above-mentioned test methods, and theresults obtained are shown in Table 2.

The comparative composition (R₁) had a low insulating resistance; andthe comparative composition (R₂) gelled after stored overnight. Thecomparative composition (R₃) gave a hardened product having cracks, andmeasurement of the insulating resistance thereof was impossible. Thecase (R₄) could not be a composition and therefore measurement of theinsulating resistance thereof was impossible.

COMPARATIVE EXAMPLE 2

In the same manner as in Example 2, comparative compositions (R₅) to(R₉) were prepared, each comprising the components shown in Table 1.These were also tested by the above-mentioned test methods, and theresults obtained are shown in Table 2.

The comparative compositions (R₅) had a low insulating resistance, and(R₆) gelled after stored overnight. (R₇) also gelled after being storedovernight. (R₈) gave a hardened product having cracks, and measurementof the insulating resistance thereof was impossible. (R₉) could not be acomposition and therefore measurement of the insulating resistancethereof was impossible.

                                      TABLE 1                                     __________________________________________________________________________           Aqueous                                                                            Aqueous Alkali                                                                         Fine Powdery                                                                          Inorganic                                               Silica Sol                                                                         Silicate Solution                                                                      Silica  Refractory Powder                                Composition                                                                          (wt. pts.)                                                                         (wt. pts.)                                                                             (wt. pts.)                                                                            (wt. pts.)                                       __________________________________________________________________________    Q.sub.1                                                                              A.sub.1                                                                         250                                                                              --       C.sub.1                                                                          150  B.sub.1                                                                         110                                            Q.sub.2                                                                              A.sub.1                                                                         250                                                                              --       C.sub.1                                                                          0.3  B.sub.1                                                                         500,                                                                              B.sub.2                                                                         500                                      Q.sub.3                                                                              A.sub.4                                                                         2000                                                                             --       C.sub.1                                                                          190  B.sub.1                                                                         200,                                                                              B.sub.2                                                                         200                                      Q.sub.4                                                                              A.sub.1                                                                         250                                                                              --       C.sub.1                                                                          20   B.sub.1                                                                         400,                                                                              B.sub.2                                                                         400                                      Q.sub.5                                                                              A.sub.4                                                                         2000                                                                             --       C.sub.1                                                                          5    B.sub.1                                                                         19000                                          Q.sub.6                                                                              A.sub.1                                                                         250                                                                              D.sub.1                                                                          120   C.sub.1                                                                          0.6  B.sub.1                                                                         600,                                                                              B.sub.2                                                                         600                                      Q.sub.7                                                                              A.sub.2                                                                         250                                                                              D.sub.1                                                                          120   C.sub.1                                                                          20   B.sub.1                                                                         400,                                                                              B.sub.2                                                                         400                                      Q.sub.8                                                                              A.sub.3                                                                         250                                                                              D.sub.1                                                                          120   C.sub.1                                                                          20   B.sub.1                                                                         400,                                                                              B.sub.2                                                                         400                                      Q.sub.9                                                                              A.sub.4                                                                         2000                                                                             D.sub.1                                                                          120   C.sub.1                                                                          20   B.sub.1                                                                         400,                                                                              B.sub.2                                                                         400                                      .sub. Q.sub.10                                                                       A.sub.2                                                                         220                                                                              D.sub.2                                                                          180   C.sub.1                                                                          20   B.sub.1                                                                         400,                                                                              B.sub.2                                                                         400                                      .sub. Q.sub.11                                                                       A.sub.2                                                                         360                                                                              D.sub.3                                                                          40    C.sub.1                                                                          20   B.sub.1                                                                         400,                                                                              B.sub.2                                                                         400                                      .sub. Q.sub.12                                                                       A.sub.2                                                                         330                                                                              D.sub.4                                                                          70    C.sub.1                                                                          20   B.sub.1                                                                         400,                                                                              B.sub.2                                                                         400                                      .sub. Q.sub.13                                                                       A.sub.2                                                                         200                                                                              D.sub.5                                                                          200   C.sub.1                                                                          20   B.sub.1                                                                         400,                                                                              B.sub.2                                                                         400                                      .sub. Q.sub.14                                                                       A.sub.1                                                                         250                                                                              D.sub.1                                                                          120   C.sub.1                                                                          20   B.sub.1                                                                         400,                                                                              B.sub.2                                                                         400                                      .sub. Q.sub.15                                                                       A.sub.1                                                                         250                                                                              D.sub.1                                                                          2000  C.sub.1                                                                          480  B.sub.1                                                                         200,                                                                              B.sub.2                                                                         200                                      .sub. Q.sub.16                                                                       A.sub.2                                                                         250                                                                              D.sub.3                                                                          0.5   C.sub.1                                                                          20   B.sub.1                                                                         250,                                                                              B.sub.2                                                                         250                                      .sub. Q.sub.17                                                                       A.sub.2                                                                         250                                                                              D.sub.1                                                                          2400  C.sub.1                                                                          80   B.sub.1                                                                         1500,                                                                             B.sub.2                                                                         1500                                     .sub. Q.sub.18                                                                       A.sub.1                                                                         250                                                                              D.sub.1                                                                          120   C.sub.1                                                                          400  B.sub.1                                                                         110                                            .sub. Q.sub.19                                                                       A.sub.4                                                                         2000                                                                             D.sub.5                                                                          10000 C.sub.1                                                                          20   B.sub.1                                                                         49000,                                                                            B.sub.2                                                                         49000                                    R.sub. 1                                                                             A.sub.1                                                                         250                                                                              --       C.sub.1                                                                          0.1  B.sub.1                                                                         500,                                                                              B.sub.2                                                                         500                                      R.sub.2                                                                              A.sub.4                                                                         2000                                                                             --       C.sub.1                                                                          220  B.sub.1                                                                         200,                                                                              B.sub.2                                                                         200                                      R.sub.3                                                                              A.sub.2                                                                         250                                                                              --       C.sub.1                                                                          150  B.sub.1                                                                         90                                             R.sub.4                                                                              A.sub.4                                                                         2000                                                                             --       C.sub.1                                                                          5    B.sub.1                                                                         21000                                          R.sub.5                                                                              A.sub.1                                                                         250                                                                              D.sub.5                                                                          200   C.sub.1                                                                          0.3  B.sub.1                                                                         600,                                                                              B.sub.2                                                                         600                                      R.sub.6                                                                              A.sub.4                                                                         2000                                                                             D.sub.2                                                                          200   C.sub.1                                                                          520  B.sub.1                                                                         200,                                                                              B.sub.2                                                                         200                                      R.sub.7                                                                              A.sub.2                                                                         250                                                                              D.sub.3                                                                          1700  C.sub.1                                                                          80   B.sub.1                                                                         1500,                                                                             B.sub.2                                                                         1500                                     R.sub.8                                                                              A.sub.1                                                                         250                                                                              D.sub.1                                                                          120   C.sub.1                                                                          400  B.sub.1                                                                         90                                             R.sub.9                                                                              A.sub.4                                                                         2000                                                                             D.sub.5                                                                          10000 C.sub.1                                                                          20   B.sub.1                                                                         51000,                                                                            B.sub.2                                                                         51000                                    __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________                             Insulating                                                                          Adhesion                                              Stability                                                                           Hardenability                                                                             Resistance                                                                          Strength                                       Composition                                                                          (gelation)                                                                          (hardness)                                                                          (cracks)                                                                            (MΩ)                                                                          (kg/cm.sup.2)                                  __________________________________________________________________________    Q.sub.1                                                                              No    Hard  No    80    18                                             Q.sub.2                                                                              "     "     "     17    18                                             Q.sub.3                                                                              "     "     "     70    20                                             Q.sub.4                                                                              "     "     "     25    17                                             Q.sub.5                                                                              "     "     "     18    17                                             Q.sub.6                                                                              No    Hard  No    22    24                                             Q.sub.7                                                                              "     "     "     110   25                                             Q.sub.8                                                                              "     "     "     110   25                                             Q.sub.9                                                                              "     "     "     20    25                                             .sub. Q.sub.10                                                                       "     "     "     27    22                                             .sub. Q.sub.11                                                                       "     "     "     60    23                                             .sub. Q.sub.12                                                                       "     "     "     70    25                                             .sub. Q.sub.13                                                                       "     "     "     35    25                                             .sub. Q.sub.14                                                                       "     "     "     100   26                                             .sub. Q.sub.15                                                                       No    Hard  No    110   24                                             .sub.  Q.sub.16                                                                      "     "     "     30    21                                             .sub. Q.sub.17                                                                       "     "     "     80    25                                             .sub. Q.sub.18                                                                       "     "     "     115   23                                             .sub. Q.sub.19                                                                       "     "     "     60    23                                             R.sub.1                                                                              No    Hard  No    1.5   20                                             R.sub.2                                                                              Yes   --          --    --                                             R.sub.3                                                                              No    Insufficient                                                                        Yes   --    --                                             R.sub.4                                                                              --    --          --    --                                             R.sub.5                                                                              No    Hard  No    1.7   21                                             R.sub.6                                                                              Yes   --          --    --                                             R.sub.7                                                                              "     --          --    --                                             R.sub.8                                                                              No    Insufficient                                                                        Yes   --    --                                             R.sub.9                                                                              --    --          --    --                                             __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________           Aqueous                                                                            Aqueous Alkali                                                                         Fine    Inorganic Silane                                        Silica Sol                                                                         Silicate Solution                                                                      Powdery Silica                                                                        Refractory Powder                                                                       Coupling Agent                         Composition                                                                          (wt. pts.)                                                                         (wt. pts.)                                                                             (wt. pts.)                                                                            (wt. pts.)                                                                              (wt. pts.)                             __________________________________________________________________________    Q.sub.20                                                                             A.sub.3                                                                         250                                                                              D.sub.4                                                                           100  C.sub.1                                                                           20  B.sub.1                                                                         400,                                                                             B.sub.2                                                                         400                                                                              E.sub.1                                                                         20                                   Q.sub.21                                                                             A.sub.2                                                                         250                                                                              D.sub.2                                                                           120  C.sub.1                                                                           25  B.sub.1                                                                         450,                                                                             B.sub.2                                                                         450                                                                              E.sub.1                                                                          2,                                                                             E.sub.5                                                                         18                               Q.sub.22                                                                             A.sub.3                                                                         500                                                                              D.sub.1                                                                           110  C.sub.1                                                                           25  B.sub.1                                                                         500,                                                                             B.sub.2                                                                         500                                                                              E.sub.1                                                                         21                                   __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________                           Insulating                                                    Stability                                                                          Hardenability                                                                            Resistance                                                                          Adhesion Strength                                Composition                                                                          (gelation)                                                                         (hardness)                                                                          (cracks)                                                                           (MΩ)                                                                          (kg/cm.sup.2)                                    __________________________________________________________________________    Q.sub.20                                                                             No   Hard  No   115   29                                               Q.sub.21                                                                             "    "     "    105   28                                               Q.sub.22                                                                             "    "     "    120   31                                               __________________________________________________________________________

EXAMPLE 4

250 parts by weight of the above-mentioned aqueous silica sol (A₁), 10parts by weight of the above-mentioned coupling agent (E₁), 370 parts byweight of the above-mentioned refractory powder (B₃) and 370 parts byweight of the above-mentioned refractory powder (B₄) were mixed in amixer for one hour at room temperature, to obtain a composition (Q₂₃) ofthe present invention.

Next, the properties of the composition (Q₂₃) were tested in accordancewith the methods mentioned above, and the results obtained are shown inTable 6 below. The thickness of the layer is also listed in the Table 6.

In the same manner, other compositions (Q₂₄) to (Q₃₃) mentioned in Table5 below were prepared and the properties thereof were tested also in thesame manner. The results obtained are shown in Table 6.

COMPARATIVE EXAMPLE 3

Comparative compositions (R₁₀) to (R₁₄) were prepared in the same manneras in Example 4, except that the components as indicated in Table 5 wereemployed. The properties of these compositions were tested in accordancewith the methods mentioned above, and the results obtained are shown inTable 6. The comparative composition (R₁₁) gelled after being storedovernight, which therefore was not tested. As being difficult, theinsulation test on (R₁₂) was not effected. Preparation of thecomposition (R₁₃) was difficult, as the proportion of the inorganicrefractory powder was too high.

The test results of all the compositions prepared in Example 4 weregood. However, the comparative composition (R₁₄) which contained nocoupling agent showed extremely low workability, hardenability, electricresistance and adhesion strength. Also in the case of the comparativecomposition (R₁₀) which contained only an extremely small amount of acoupling agent, it was found that the workability, hardenability,electric resistance and adhesion strength of the composition were notimproved. As containing too less or too much refractory powder,respectively, the comparative compositions (R₁₂) and (R₁₃) could nothave sufficiently improved workability and hardenability.

                  TABLE 5                                                         ______________________________________                                        Proportion of Ingredients                                                     Compo-                Coupling     Refractory                                 sition Sol    wt. pts.                                                                              Agent  wt. pts.                                                                            Powder  wt. pts.                           ______________________________________                                        Q.sub.23                                                                             A.sub.1                                                                              250     E.sub.1                                                                              10    B.sub.3 370                                                                   B.sub.4 370                                Q.sub.24                                                                             A.sub.2                                                                              250     E.sub.1                                                                              10    B.sub.3 370                                                                   B.sub.4 370                                Q.sub.25                                                                             A.sub.2                                                                              250     E.sub.2                                                                              10    B.sub.3 370                                                                   B.sub.4 370                                Q.sub.26                                                                             A.sub.2                                                                              250     E.sub.3                                                                              10    B.sub.3 370                                                                   B.sub.4 370                                Q.sub.27                                                                             A.sub.2                                                                              250     E.sub.4                                                                              10    B.sub.3 370                                                                   B.sub.4 370                                Q.sub.28                                                                             A.sub.2                                                                              250     E.sub.5                                                                              10    B.sub.3 370                                                                   B.sub.4 370                                Q.sub.29                                                                             A.sub.2                                                                              250     E.sub.1                                                                              10    B.sub.3 740                                Q.sub.30                                                                             A.sub.2                                                                              250     E.sub.1                                                                              10    B.sub.4 740                                Q.sub.31                                                                             A.sub.3                                                                              250     E.sub.2                                                                              10    B.sub.3 370                                                                   B.sub.4 370                                Q.sub.32                                                                             A.sub.4                                                                              2000    E.sub.1                                                                              490   B.sub.3 2500                                                                  B.sub.4 2500                               Q.sub.33                                                                             A.sub.2                                                                              250     E.sub.1                                                                              0.06  B.sub.3 370                                                                   B.sub.4 370                                Q.sub.34                                                                             A.sub.4                                                                              2000    E.sub.1                                                                              100   B.sub.3 4500                                                                  B.sub.4 4500                               Q.sub.35                                                                             A.sub.2                                                                              250     E.sub.1                                                                              10    B.sub.3  30                                                                   B.sub.4  30                                R.sub.10                                                                             A.sub.2                                                                              2500    E.sub.1                                                                              0.04  B.sub.3 370                                                                   B.sub.4 370                                R.sub.11                                                                             A.sub.4                                                                              2000    E.sub.1                                                                              550   B.sub.3 2500                                                                  B.sub.4 2500                               R.sub.12                                                                             A.sub.2                                                                              250     E.sub.1                                                                              10    B.sub.3  20                                                                   B.sub.4  20                                R.sub.13                                                                             A.sub.4                                                                              2000    E.sub.1                                                                              100   B.sub.3 5500                                                                  B.sub.4 5500                               R.sub.14                                                                             A.sub.1                                                                              250     --     0     B.sub.3 370                                                                   B.sub.4 370                                ______________________________________                                    

                                      TABLE 6                                     __________________________________________________________________________                                  Electric                                                                            Adhesion Strength                                Stability                                                                          Workability                                                                          Hardenability                                                                            Resistance (thickness,                          Composition                                                                          (fluidity)                                                                         (flocculation)                                                                       (hardness)                                                                          (cracks)                                                                           (MΩ)                                                                          (kg/cm.sup.2)                                                                      mm)   (breakage)                     __________________________________________________________________________    Q.sub.23                                                                             Yes  No     Hard  No    5    25   0.35  L                              Q.sub.24                                                                             Yes  No     Hard  No   5-10  36   0.35  L                              Q.sub.25                                                                             Yes  No     Hard  No    5    33   0.35  L                              Q.sub.26                                                                             Yes  No     Hard  No   10    21   0.35  L                              Q.sub.27                                                                             Yes  No     Hard  No   10    20   0.35  L                              Q.sub.28                                                                             Yes  No     Hard  No   5-10  30   0.35  L                              Q.sub.29                                                                             Yes  No     Hard  No   5-10  36   0.35  L                              Q.sub.30                                                                             Yes  No     Hard  No   5-10  35   0.35  L                              Q.sub.31                                                                             Yes  No     Hard  No   15    20   0.35  L                              Q.sub.32                                                                             Yes  No     Hard  No   15    18   0.1   L                              Q.sub.33                                                                             Yes  No     Hard  No    5    15   0.35  L                              Q.sub.34                                                                             Yes  No     Hard  No    5    25   0.35  L                              Q.sub.35                                                                             Yes  No     Hard  No    5    30   0.1   L                              R.sub.10                                                                             Yes  Yes    Insufficient                                                                        Yes   1    10   0.35  S                              R.sub.11                                                                             No   --     --    --   --    --   --    --                             R.sub.12                                                                             Yes  No     Insufficient                                                                        Yes  --    26   0.1   L                              R.sub.13                                                                             No   --     --    --   --    --   --    --                             R.sub.14                                                                             Yes  Yes    Insufficient                                                                        Yes  1 or less                                                                            5   0.35  S                              __________________________________________________________________________

EXAMPLE 5

One end of a stainless steel wire having a thickness of 1 mm wasinserted into the joint part of a ceramic insulator joint, and the jointpart was filled with the composition (Q₃₅) as prepared in Example 4.This was then dried in a drier at 110° C. for 30 minutes and then at200° C. for 30 minutes, whereby the wire and the insulator were bondedto each other. Next, a tension of 50 kg was imparted to the insulatorand the stainless steel wire, but the bonded part was not broken.

EXAMPLE 6

An aqueous silica sol, an aqueous alkali silicate solution, a finepowder silica, an inorganic refractory powder and a silane couplingagent, which are indicated in Table 7 below, were mixed for 3 hours atroom temperature, to prepare compositions (Q₃₆) to (Q₃₉) mentioned inTable 7.

Next, the properties of these compositions (Q₃₆) to (Q₃₉) and those ofthe hardened products thereof were tested in accordance with theabove-mentioned test methods. The results obtained are shown in Table 8below.

                                      TABLE 7                                     __________________________________________________________________________           Aqueous                                                                            Aqueous Alkali                                                                         Fine    Inorganic Silane                                        Silica Sol                                                                         Silicate Solution                                                                      Powdery Silica                                                                        Refractory Powder                                                                       Coupling Agent                         Composition                                                                          (wt. pts.)                                                                         (wt. pts.)                                                                             (wt. pts.)                                                                            (wt. pts.)                                                                              (wt. pts.)                             __________________________________________________________________________    Q.sub.36                                                                             A.sub.1                                                                         250                                                                              --       C.sub.1                                                                           30  B.sub.1                                                                         750,                                                                             B.sub.2                                                                         750                                                                              E.sub.2                                                                           30                                 Q.sub.37                                                                             A.sub.2                                                                         250                                                                              --       C.sub.1                                                                           40  B.sub.1                                                                         500,                                                                             B.sub.2                                                                         500                                                                              E.sub.5                                                                           25                                 Q.sub.38                                                                             A.sub.1                                                                         250                                                                              D.sub.1                                                                           200  --      B.sub.1                                                                         600,                                                                             B.sub.2                                                                         600                                                                              E.sub.2                                                                           25                                 Q.sub.39                                                                             A.sub.3                                                                         500                                                                              D.sub.2                                                                           220  --      B.sub.1                                                                         700,                                                                             B.sub.2                                                                         700                                                                              E.sub.4                                                                           30                                 __________________________________________________________________________

                                      TABLE 8                                     __________________________________________________________________________                           Insulating                                                    Stability                                                                          Hardenability                                                                            Resistance                                                                          Adhesion Strength                                Composition                                                                          (gelation)                                                                         (hardness)                                                                          (cracks)                                                                           (MΩ)                                                                          (kg/cm.sup.2)                                    __________________________________________________________________________    Q.sub.36                                                                             No   Hard  No   95    21                                               Q.sub.37                                                                             No   Hard  No   97    20                                               Q.sub.38                                                                             No   Hard  No   31    26                                               Q.sub.39                                                                             No   Hard  No   25    25                                               __________________________________________________________________________

The adhesive composition of the present invention can be prepared withease and it may simply be hardened by drying at room temperature or byheating up to a temperature of approximately 300° C. to give a hardenedproduct having a noticeably improved electric insulating property.Accordingly, it may advantageously be used for adhesion of materials ofthe same kind or different kinds which are required to have a highinsulating property, such as ceramics, glass, slates, hardened cementproducts, aluminium stainless steel, iron and other metal materials,whereupon the bonded part displays an extremely improved electricinsulating property and mechanical strength. Additionally, the adhesivecomposition of the present invention may also be used for adhesion of ametal plate and a ceramic fiber mat and for adhesion of mortar plates.

As other advantageous merits, the composition of the present inventionhas a sufficient storage stability for an extremely long period of timeand has excellent fluidity and workability in operation of adhesion orcoating with the composition. Additionally, after hardened, thecomposition gives a hardened adhesive product which neither cracks norshrinks. Even when repeated heat-shocks are applied to the hardenedadhesive product, the bonded part is not broken. That is, the hardenedproduct from the composition of the invention has an extremely excellentheat shock-resistance. Therefore, the composition of the invention mayconveniently be used for adhesion of various electric parts orelectronic parts, such as sensor, as well as other various parts ofelectric or electronic appliances.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A method of bonding together materials of thesame kind or different kinds selected from the group consisting ofceramics, glass, slates, hardened cement products and metal materials,comprising (1) putting between and in contact with two adjacent surfacesof said materials an adhesive composition comprising:(a) an aqueoussilica sol having a mean particle size of from 5 to 200 millimicrons anda molar ratio of SiO₂ /M₂ O (where M represents an alkali metal atom, anamine molecule, or a quaternary ammonium group) of from 30 to 2000, inan amount of 100 parts by weight as SiO₂ ; (b) an inorganic refractorypowder having a particle size of from 0.5 to 1000 microns, in an amountof from 100 to 100000 parts by weight; (c) a fine powdery silica inamorphous form having a particle size of from 5 to 200 millimicrons, inan amount of from 0.5 to 500 parts by weight; (d) an aqueous solution ofan alkali silicate having a molar ratio of SiO₂ /M'₂ O (where M'represents Na, K, Li, an amine molecule, or a quaternary ammonium group)of from 1 to 30 and having an alkali silicate concentration of from 1 to60% by weight, in an amount of from 0.1 to 500 parts by weight as thealkali silicate component; and (e) one or more coupling agents selectedfrom the group consisting of a silane compound of a general formula (I):

    R.sup.1 Si(OR).sub.3                                       (I)

where OR represents an alkoxy or acyloxy group having from 1 to 3 carbonatoms, and R¹ represents a monovalent organic group having from 2 to 9carbon atoms, or a hydrolysate thereof, and a silane compound of ageneral formula (II):

    R.sup.1 SiCH.sub.3 (OR).sub.2                              (II)

whereOR and R¹ have the same meanings as defined above, or a hydrolysatethereof, in an amount of from 0.05 to 100 parts by weight; the solidcontent of the components (a), (b), (c), (d) and (e) being from 40 to95% by weight; said composition having a viscosity of from 1 to 10000poise at 20° C.;(2) drying and hardening said composition between saidsurfaces at a temperature higher than the freezing temperature of thecomposition not to exceed 300° C.
 2. The method as claimed in claim 1,in which the drying is effected at a temperature of 80° to 300° C.
 3. Amethod as claimed in claim 1, wherein said aqueous silica sol (a) has amean particle size of from 10 to 150 millimircorns and has an SiO₂concentration of from 1 to 50% by weight and in which M is selected fromthe group consisting of Na, K, Li, methylamine, ethylamine,ethanolamine, tetramethylammonium, monomethyltriethanolammonium,isopropyltriethanolammonium, and tetraethanolammonium.
 4. A method asclaimed in claim 1, wherein said inorganic refractory powder (b)comprises at least one member selected from the group consisting ofpowder of quartz, powder of silica, powder of feedspar, powder ofaluminum silicate, powder of zirconium silicate, powder of mullite,powder of zirconia, powder of alumina, powder of silicon nitride, powderof silicon carbide, powder of talc, powder of mica, fibrous powder ofglass fiber and fibrous powder of potassium titanate fiber.
 5. A methodas claimed in claim 1, wherein said aqueous alkali silicate solution (d)has a molar ratio of SiO₂ /M'₂ O of from 1 to 10 and has an alkalisilicate concentration of from 5 to 50% by weight and wherein M' isselected from the group consisting of Na, K, Li, methylamine,ethylamine, ethanolamine, tetramethylammonium,monomethyltriethanolammonium, isopropyltriethanolammonium andtetrathanolammonium.
 6. A method as claimed in claim 1, wherein saidcoupling agent (e) comprises at least one member selected from the groupconsisting of vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane,vinyltrimethoxysilane, vinyltriacetoxysilane,γ-methacryloxypropyltrimethoxysilane,β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropylmethyldiethoxysilane,N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane,γaminopropyltriethoxysilane, γ-anilinopropyltrimethoxysilane, andhydrolysates of the silanes recited in said group.